[ms-inline asm] Refactor/clean up the SemaLookup interface.  No functional
change indended.
Part of rdar://13663589
[ms-inline asm] Refactor/clean up the SemaLookup interface.  No functional
change indended.
Part of rdar://13663589
Fix for expression/breakpoint setting of gnu indirect functions.

Do this until we are able to resolve these symbols to their actual implementations without needing runtime support.